1. Field of the Invention
The present invention relates to a memory fault recovery system which executes recovery of a fault memory in a processing unit (CPU:central processing unit) constituting an information processor.
2. Description of the Related Arti
A conventional fault or failure recovery system of this kind is recited in, for example, Japanese Patent Laying-Open No. 41943/1988. Under the fault recovery system, when a memory fault is found in a processing unit and if degradation of the function is possible, the part at fault is immediately degraded to try another execution of the operation of the unit.
In this fault recovery method, if the part at fault in a processing unit can be degraded, degradation operation immediately follows the degradation processing. This method therefore has a disadvantage in that degradation of function is always executed even for a fault requiring no degradation.
In recent years, as the integration density of memories has grown, intermittent faults derived from soft errors are found in memories more frequently. In many instances, such intermittent memory faults can be overcome by rewriting the memory. Unconditional degradation of such memory whose fault is recoverable would lead to low system performance. On the other hand, the above-described degradation has no drawback for a fault found in parts of a processing unit other than other memories, because in many cases such fault is not an intermittent but fixed one whose recovery is hard.